CN113685841B - Working medium supply system for wind tunnel experiment heat storage heater and construction method - Google Patents

Abstract

The invention belongs to the technical field of aerospace ground test equipment, and aims to solve the technical problem of reduced structural strength of a heat storage tank in the prior art, and provides a working medium supply system for a wind tunnel experiment heat storage heater and a construction method thereof, wherein a natural gas point path and an air point path are respectively connected with an igniter, and the igniter is controlled to ignite through the natural gas point path and the air point path; the natural gas main path, the air main path and the oxygen supplementing path are respectively connected with the main burner, the wide-range flow is regulated through the natural gas main path and the air main path, and the oxygen supplementing path is used for providing oxygen supplementation during high-temperature large flow; the cooling air path is connected with the cooling burner; the total pressure of the igniter is measured through a pressure sensor, and the main flame of the burner is detected through a flame detector. The invention can realize the function of stepless regulation of flow in the measuring range, and avoids the possibility of ceramic material damage caused by over-quick heating temperature rise and the risk of structural strength reduction of the heat storage tank body caused by local overheating during heating.

Description

A working fluid supply system and construction method for a regenerative heater in a wind tunnel experiment

technical field

The invention belongs to the technical field of aerospace ground test equipment, and in particular relates to a working fluid supply system and a construction method for a regenerative heater in a wind tunnel experiment.

Background technique

The pure air wind tunnel can provide relatively clean high-enthalpy gas flow, which is an indispensable equipment for the ground test of hypersonic aircraft, and has been widely recognized in the world. However, due to the technical difficulty, few pure air wind tunnels have been successfully developed at home and abroad. Among them, the working fluid supply system is one of the technical difficulties. As shown in Figure 1, the regenerative heating process is as follows: the computer control system controls the working medium supply system to provide natural gas and air for the burner, the igniter ignites the natural gas to form a low-power torch, and the torch ignites the working medium supply system. The main road natural gas and air form a high temperature flame, which heats the main regenerator to a preset temperature through heat exchange. During the wind tunnel test, cold air enters from the bottom to exchange heat with the regenerator, and obtains clean air with high temperature and high pressure of about 1700K and 5MPa. There are two difficulties in the design of the working medium supply system in the regenerative heating process: 1) There are strict requirements for the adjustment of the working medium flow. At present, the main body of heat storage can only use ceramic materials whose melting point can be higher than 2000K. However, the thermal shock resistance of ceramics is very poor, and there are strict requirements for the temperature change of the burner flame. If the temperature rises too fast, the ceramic material will be cracked or even crushed. The heat storage tank also has strict requirements on the change of flame power. It is necessary to avoid local overheating inside the heat storage tank, otherwise the structural strength of the heat storage tank will be reduced, resulting in irreparable losses. It can be seen from the combustion science that the temperature and power of the flame is the problem of matching the flow of the working medium supply. The working medium supply system is required to have the ability to adjust the flow, and the higher the adjustment resolution, the better. 2) The working fluid supply system should have the ability to provide cooling air for the burner. During the charging process of wind tunnel operation (high back pressure and no combustion state), it is necessary to prevent the heat accumulator from damaging the inner wall of the burner by radiant heat; the structural cooling problem of the burner itself in a high temperature environment.

In view of the above reasons, the current technical method is to prepare multiple current-limiting devices with different diameters in advance, control the on-off of the front-end switch valve, and realize the adjustment of the working fluid flow through different combinations. This method preliminarily realizes the stepwise adjustment of the working fluid flow, but the method is not flexible enough, the adjustable range is limited, and the accuracy cannot be guaranteed. The ability to reheat depending on the tank temperature. In addition, the current regenerative burner is basically a water-cooled solution. The biggest risk of water cooling is that once it leaks, the regenerative material will burst when it encounters water, the cooling water will instantly vaporize when it is heated, and the pressure in the regenerative tank will increase sharply, and the consequences will be catastrophic. .

SUMMARY OF THE INVENTION

In view of the existing technical problems in the prior art that the heating temperature rises too fast and the ceramic material is damaged due to the inability of the working medium supply system to achieve wide-range continuous adjustment, and the structural strength of the heat storage tank is reduced due to the local overheating of heating, the present invention The purpose of the invention is to provide a working fluid supply system and a construction method for a regenerative heater in a wind tunnel experiment.

The technical scheme adopted in the present invention is:

A working medium supply system for a regenerative heater in a wind tunnel experiment, comprising a natural gas point circuit, an air point circuit, a natural gas main circuit, an air main circuit, an oxygen supplementary circuit (referred to as oxygen circuit), a cooling air circuit (referred to as air cooling), and a pressure sensor and flame detectors;

The natural gas point circuit, the air point circuit, the natural gas main circuit, the air main circuit, the oxygen supplementary circuit, and the cooling air circuit are provided with a shut-off valve before and after each pressure regulating valve, which is a valve for each circuit (the first switch valve) , Two valves for each channel (the second switch valve);

The natural gas point road and the air point road are respectively connected with the igniter, and the natural gas point road and the empty point road are used to deliver a constant flow of natural gas and air to the igniter;

The natural gas main circuit, the air main circuit, and the oxygen supplementary circuit (referred to as the oxygen circuit) are respectively connected with the main burner, and the wide-range flow rate is adjusted through the natural gas main circuit and the air main circuit. Provide oxygen input under working conditions;

The cooling air path is connected with the burner cooling channel; the total pressure of the igniter is measured by a pressure sensor, and the main flame of the burner is detected by a flame detector.

Further, the natural gas point circuit and the air point circuit have the same structure, and both include a gas pipeline, a sensor, a pressure reducing valve, a throttling device, and a check valve. The sensor is arranged before a valve, and the gas is measured by the sensor. The pressure reducing valve is arranged between the first valve and the second valve, the rear end of the second valve is connected to the throttling device, the end of the gas pipeline is connected to the check valve near the burner interface, and the downstream of the check valve is connected to the burner.

Further, the natural gas point road and the air point road have the same structure, and both include a gas transmission pipeline for conveying the working fluid, and the sensor a and the sensor b of the natural gas point road for measuring the pressure of the gas source are respectively provided with a valve a and a valve. Before b, the pressure reducing valve a and the pressure reducing valve b are arranged between the two shut-off valves. The rear ends of the second valve a and the second valve b are respectively connected to the throttle device a and the throttle device b, and the end of the gas pipeline is close to the burner interface. The check valve a and the check valve b are connected to the burner respectively, and the downstream of the check valve a and the check valve b are connected to the burner.

Further, the igniter is set as a fixed power igniter, the natural gas point circuit and the air point circuit use a fixed value pressure reducing valve, and the natural gas point circuit and the air point circuit output a medium with a fixed flow and pressure, and the system is realized by controlling the stop valve switch. The medium output is on and off.

Further, the natural gas main circuit and the air main circuit include multiple branches with different flow coefficients, and the branches are increased or decreased according to actual needs. The sensor, the sensor for measuring the pressure of the air source is arranged in front of a valve, and there are multiple branch pipelines behind a valve. Each branch includes a pressure regulating valve group, a sensor group for measuring the pressure behind the valve and a throttling device. The group adjusts the medium pressure. A sensor for measuring the pressure behind the valve is installed downstream of the pressure regulating valve group. The rear end of the second valve is connected to a throttling device. After the throttling device, each branch is merged into a pipeline. Connect the check valve, downstream of the check valve to the burner.

Further, the natural gas main road and the air main road mainly include multiple branches with different flow coefficients. Both the natural gas main road and the air main road include pipelines for conveying the working medium. The sensors c and d for measuring the pressure of the gas source are arranged before a valve c and a valve d, and a valve c and a valve d are divided into multiple A branch pipeline, each branch includes pressure regulating valve c, pressure regulating valve d, pressure regulating valve e and pressure regulating valve f, pressure regulating valve c, pressure regulating valve d, pressure regulating valve e and pressure regulating valve The downstream of the pressure valve f are respectively installed with a sensor e, a sensor f, a sensor g and a sensor h for measuring the pressure behind the valve. The second valve c, the second valve d, the second valve e and the second valve f are respectively connected to the throttling device c and the throttling device. d. Throttle device e and throttle device f. Each branch is merged into a pipeline after the throttle device, the end of the gas pipeline is connected to the check valve c and the check valve d near the burner interface, and the downstream of the check valve c and the check valve d is connected to the burner.

Preferably, the natural gas main circuit and the air main circuit of the present invention are a combination of multiple branches with different flow coefficients, and the branches can be increased or decreased according to actual needs. The design can flexibly adjust the number of branches to achieve a wide range of flow regulation functions.

Further, the oxygen supplementary circuit (abbreviated as oxygen circuit) includes a gas pipeline, a pressure regulating valve g, a sensor i, a sensor j, a throttle device g, and a check valve e, and the sensor i for measuring the pressure of the gas source is provided at Before the first valve e, the pressure regulating valve g is arranged between the first valve e and the second valve f. A sensor j for measuring the pressure behind the valve is installed downstream of the pressure regulating valve g. After the second valve f is connected to the throttling device g, the end of the gas pipeline The check valve e is connected to the interface of the burner, and the check valve e is connected to the main air circuit through a tee.

Preferably, the oxygen path and the main air path are connected before entering the burner. The purpose of this design is to prolong the mixing process, make the mixing more uniform, and improve the combustion efficiency.

Further, the cooling air circuit (referred to as air cooling) includes a gas pipeline, a sensor k, a valve f, a pressure regulating valve h, a sensor 1, a second valve g, a throttling device h, an on-off valve a, and an on-off valve b. , check valve f, the sensor k for measuring the pressure of the air source is set before the first valve f, the pressure regulating valve h is set between the first valve f and the second valve g, and the downstream of the pressure regulating valve h is installed with a sensor l measuring the pressure behind the valve , the rear end of the second valve g is connected to the throttling device h, the end of the gas pipeline is connected to the burner cooling channel inlet near the burner interface, the burner cooling channel outlet is connected to a switch valve a through the pipeline, and the rear end of the switch valve a is connected through the pipeline discharge to the outside;

The cooling air path (referred to as air cooling) is divided into two paths at the outlet of the cooling passage of the burner through a three-way, one path is connected to an on-off valve c and leads to the outside; between valve d and the burner.

Further, the throttling device cooperates with the upstream pressure regulating valve to control the flow regulation in the range of the single branch, and the throttling device is set as a special device based on the sonic nozzle. Upstream piping, pressure chamber, sonic nozzle, downstream piping. The chamber is provided with a pressure sensor and a temperature sensor, and the control of the pipeline flow is transformed into the regulation of the chamber pressure through the throttling device. The gas pressure and temperature are respectively measured by a pressure sensor and a temperature sensor; the purpose of this design is to stabilize the incoming flow pressure and convert the difficult-to-obtain gas flow into easily measurable pressure data and temperature data.

Further, the pressure regulating valve and the downstream pressure sensor form a closed loop, and the output value of the pressure regulating valve is adjusted in real time according to the data of the pressure sensor. The purpose of this design is to achieve accurate output of its own pressure through downstream pressure feedback, thereby improving the accuracy of pipeline flow regulation. Furthermore, after the wind tunnel test, the flame temperature can be precisely controlled according to the set working conditions of the temperature in the tank, so as to realize the ability of reheating. It greatly improves the test efficiency and saves resources.

The valves in contact with the working medium are all set as pneumatic valves driven by nitrogen. The purpose of this design is to isolate the combustible gas from air (or oxygen), and to isolate the combustible gas from the circuit, so as to avoid the possibility of danger to the greatest extent.

A construction method for supplying working medium for a heat storage heater in a wind tunnel experiment, adopting the working medium supply system for a heat storage heater in a wind tunnel experiment, specifically comprising the following steps:

(1) According to the test requirements, determine the flow value or range required for each gas supply;

(2) Determine the value range and the number of branches of the Venturi flowmeter of each main circuit or branch according to the temperature of the gas supply, the pressure of the gas source, and the pressure of the combustion chamber;

(3) Select the diameter of the flowmeter, and calculate the pressure regulating value or range of the upstream pressure regulating valve;

(4) Determine the diameter of the pipeline and the on-off valve and the Cv value of the pressure regulating valve according to the maximum flow of each branch.

Further, in the step (2), the natural gas point and the empty point Venturi flowmeter path DN are determined according to the supply gas temperature T ₀ , the gas path gas source pressure P ₀ , and the combustion chamber pressure P, and the natural gas main path, the air The number N of each branch circuit of the main circuit and the air-cooling circuit and the diameter DN of each Venturi flowmeter, for the gas flow with the sound velocity in the throat, it conforms to the relationship:

In the formula, Q _m is the mass flow rate; C is the outflow coefficient; P ₀ is the absolute stagnation pressure at the inlet; T ₀ is the absolute stagnation temperature at the inlet; D is the throat diameter of the venturi flowmeter; Calculate the throat diameter range.

The beneficial effects of the present invention are:

The invention provides a working fluid supply system and a construction method for a regenerative heater in a wind tunnel experiment, which can realize the function of stepless adjustment of flow within a range, avoid the possibility of damage to ceramic materials caused by excessive heating temperature rise, and The local overheating of heating brings the risk of reducing the structural strength of the thermal storage tank. The typical working conditions are precisely controlled, and the ability to reheat according to the temperature of the tank after the wind tunnel test is realized. Greatly improve the test efficiency. The cooling air with adjustable flow rate is provided for the burner under the condition of high back pressure and no combustion, and the damage of the burner by heat radiation is avoided. The gas cooling of the burner's own structure is realized, the reliability of the equipment is improved, and the cooling gas can continue to be used for the main road air to participate in the combustion, saving energy. The invention has clear principle, simple structure and easy realization, and has extremely high application value.

Description of drawings

1 is a schematic diagram of the working process of a regenerative heater in the prior art;

2 is a schematic diagram of a working medium supply system in the present invention;

3 is a schematic diagram of a throttling device based on a Venturi flowmeter in the present invention;

4 is a structural step diagram of a working medium supply system in the present invention;

Fig. 5 is the test data diagram of the embodiment in the present invention;

Among them, 00, igniter; 01, flame detector; 2, burner;

11, sensor a; 12, sensor c; 13, sensor k; 14, sensor b; 15, sensor i; 16, sensor d; 17, total pressure sensor; 21, a valve a; 22, a valve c; 23, A valve f; 24, a valve b; 25, a valve e; 26, a valve d;

31. Pressure reducing valve a; 32. Pressure reducing valve b;

41, pressure regulating valve c; 42, pressure regulating valve d; 43, pressure regulating valve h; 44, pressure regulating valve g; 45, pressure regulating valve e; 46, pressure regulating valve f;

51, sensor e; 52, sensor f; 53, sensor j; 54, sensor g; 55, sensor h; 56, sensor l;

61, two valves a; 62, two valves c; 63, two valves d; 64, two valves g; 65, two valves b; 66, two valves f; 67, two valves e; 68, two valves f; 69, On-off valve a;

71, throttle device a; 72, throttle device c; 73, throttle device d; 74, throttle device h; 75, throttle device b; 76, throttle device g; 77, throttle device e; 78 701, upstream pipeline; 702, pressure stabilization chamber; 703, sonic nozzle; 704, downstream pipeline; 705, pressure sensor; 706, temperature sensor;

81, check valve c; 82, check valve a; 83, check valve b; 84, check valve e; 85, check valve d;

91. On-off valve b; 92. On-off valve c;

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

Example 1

As shown in Figure 2, according to the wind tunnel test requirements, the regenerative heater needs to provide high temperature and high pressure airflow with a temperature of 1200K-1600K and a maximum flow rate of 10kg/s. In order to achieve the technical requirements, alumina is selected as the porous regenerative ceramic material. In order to uniformly heat and exchange heat, the regenerative ceramic adopts a multi-layer concentric arrangement of circular holes. The main material of heat storage adopts the accumulation volume of 0.8 meters in diameter and 5 meters in height. Due to the thermal shock resistance properties of alumina, it is required that the temperature rise per hour should not exceed 80 °C. The burner 2 of the embodiment works at atmospheric pressure, that is, the combustion pressure is 0.1 MPa. During the wind tunnel test, the maximum pressure when filling air in the heat storage tank is 5MPa, that is, the pressure is not less than 5MPa when the high back pressure is not in the combustion state. At this time, 100g/s of cooling air is required for the burner 2 with a power of about 600kW, stepless Adjustable large ratio (10:1) stable combustion of flame under variable power. The specific description is as follows in conjunction with the embodiment:

This embodiment includes a natural gas point circuit and an air point circuit for the igniter 00; a natural gas main circuit and an air main circuit (referred to as the air main circuit) for the main burner 2 with wide-range flow adjustment, which are used for cooling the burner 2. The cooling air circuit of the main body (referred to as air cooling) is used for the oxygen supplementary circuit (referred to as oxygen circuit) at high temperature and large flow. Also included are a total pressure sensor 17 for measuring the total pressure of the igniter, a flame detector 01 for detecting the main flame of the burner 2, and a PLC based control system.

On the basis of Embodiment 1, another embodiment of the present invention, as shown in FIG. 2 , has the same structure of the natural gas point circuit and the air point circuit of this embodiment.

The natural gas point road includes a gas transmission pipeline for conveying working fluid, the sensor a11 for measuring the pressure of the gas source is arranged in front of the first valve a21, the pressure reducing valve a31 is arranged between the two on-off valves composed of the first valve a21 and the second valve a61, The rear end of the second valve a61 is connected to the throttle device a71, the end of the gas pipeline is connected to the check valve a82 near the interface of the burner 2, and the downstream of the check valve a82 is connected to the burner 2.

The air point circuit includes an air pipeline for conveying the working medium. The sensor b14 for measuring the pressure of the air source is arranged before the first valve b24, the pressure reducing valve b32 is arranged between the two on-off valves, and the rear end of the second valve b65 is connected to the throttling device. b75, the end of the gas transmission pipeline is connected to the check valve b83 near the interface of the burner 2, and the downstream of the check valve b83 is connected to the burner 2.

On the basis of Embodiment 1, another embodiment of the present invention, as shown in FIG. 2 , the igniter involved in this embodiment is a fixed power igniter, and the natural gas point circuit and the empty point circuit only need to output a fixed flow and pressure Therefore, the natural gas point circuit and the empty point circuit are designed as fixed value pressure reducing valves, and the computer control system realizes the medium output on and off by controlling the shut-off valve switch. The advantage of this is that the control loop is reduced, the structure is simplified, the system reliability is improved, and the cost is reduced.

In another embodiment of the present invention, as shown in FIG. 2 , the natural gas main circuit in this embodiment includes two branches with different flow coefficients, the natural gas main circuit includes a pipeline for conveying working fluid, and a sensor for measuring the pressure of the gas source. c12 is set before a valve c22, the first road and the second road are connected in parallel, and a valve c22 is set as two branch pipelines;

The first branch includes a pressure regulating valve c41, a sensor e51, a second valve c62, and a throttling device c72. A sensor e51 for measuring the pressure behind the valve is installed downstream of the pressure regulating valve c41 that adjusts the medium pressure, and the second valve c62 is connected to the throttling device c72. ;

The second branch includes a pressure regulating valve d42, a sensor f52, a second valve d63, and a throttling device d73. A sensor f52 for measuring the pressure behind the valve is installed downstream of the pressure regulating valve d42 that adjusts the medium pressure, and the second valve d63 is connected to the throttling device d73. .

The first branch and the second branch are merged into one pipeline after the throttle device c72 and the throttle device d73. The end of the gas pipeline is connected to the check valve c81 near the interface of burner 2, and the downstream of the check valve c81 is connected to the burner 2.

As shown in FIG. 2 , the main air circuit in this embodiment mainly includes multiple branches with different flow coefficients, the main air circuit includes an air pipeline for conveying working fluid, and a sensor d16 for measuring the pressure of the air source is provided in a valve d26 In the front, a valve d26 is divided into 2 branch pipelines in the rear;

The first branch includes a pressure regulating valve e45 for adjusting the pressure of the medium, a sensor g54 for measuring the pressure behind the valve is installed downstream of the pressure regulating valve e45, and the second valve e67 is connected to a throttling device e77;

The second branch includes a pressure regulating valve f46 for adjusting the pressure of the medium, a sensor h55 for measuring the pressure behind the valve is installed downstream of the pressure regulating valve f46, and a throttling device f78 is connected behind the second valve f68;

The first branch and the second branch are merged into one pipeline after the throttle device e77 and the throttle device f78. The end of the gas pipeline is connected to the check valve d85 near the interface of burner 2, and the downstream of the check valve d85 is connected to the burner 2.

Further, the natural gas main circuit and the air main circuit of the present invention are a combination of multiple branches with different flow coefficients, and the branches can be increased or decreased according to actual needs. The advantage of this is that the number of branches can be flexibly adjusted to achieve a wide range of flow adjustment functions.

On the basis of Embodiment 1, in another embodiment of the present invention, as shown in FIG. 2 , the oxygen circuit of the present invention includes a gas transmission pipeline for conveying the working medium, and the sensor i15 for measuring the pressure of the gas source is arranged in a valve e25 Before, the pressure regulating valve g44 is arranged between the two on-off valves consisting of a valve e25 and a second valve f66, a sensor j53 for measuring the pressure behind the valve is installed downstream of the pressure regulating valve g44, and a throttle device g76 is connected behind the second valve f66, and the output is The end of the air pipeline is connected to the check valve e84 near the interface of the burner 2, and the check valve e84 is connected to the main air circuit through a tee.

Further, the oxygen path and the air main path are connected before entering the burner 2, which has the advantage of prolonging the mixing process, making the mixing more uniform, and improving the combustion efficiency.

On the basis of Embodiment 1, in another embodiment of the present invention, as shown in FIG. 2 , the air-cooling circuit of the present invention includes a gas transmission pipeline for conveying the working medium, and the sensor k13 for measuring the pressure of the gas source is arranged in a Before the valve f23, the pressure regulating valve h43 is arranged between the two on-off valves composed of the first valve f23 and the second valve g64. A sensor l56 for measuring the pressure after the valve is installed downstream of the pressure regulating valve h43, and the second valve g64 is connected to the throttling device h74. , the gas transmission pipeline is directly connected to the inlet of the cooling channel of the burner 2, the outlet of the cooling channel of the burner 2 passes through a valve a69 of the pipeline, and after the valve a69 is switched on and off, it is discharged to the outdoor through the pipeline.

On the basis of Embodiment 1, in another embodiment of the present invention, as shown in FIG. 2 , the air-cooling circuit of the present invention is divided into two paths at the outlet of the cooling passage of the burner 2 through a three-way, and one is connected to an on-off valve c92 leading to the outdoor. ; The other road is connected to the main air check valve d85 and the burner 2 after passing through a switch valve b91. The air used in the air cooling circuit to cool the burner 2 can again provide a large flow of air for the air master through the above structure. The advantage of this is that it provides a large flow of air for the main air circuit, realizes the reuse of air in the air cooling circuit, and saves energy; effectively reduces the branches of the main air circuit, simplifies the structure, improves system reliability, and reduces costs. .

On the basis of Embodiment 1, in another embodiment of the present invention, the throttling device used in the present invention is set as a special device based on sonic nozzles. As shown in FIG. 3 , the device is followed by the upstream pipeline 701 , the stable Pressure chamber 702 , sonic nozzle 703 , downstream pipeline 704 . A pressure sensor 705 and a temperature sensor 706 that can measure the gas pressure and temperature are integrated on the plenum chamber 702 . The advantage of this structure is to stabilize the incoming flow pressure and improve the flow control accuracy of the sonic nozzle. In addition, regulation of line flow is converted into regulation of chamber pressure by this device. It cooperates with the upstream pressure regulating valve to realize flow regulation in the range of a single branch.

On the basis of Embodiment 1, in another embodiment of the present invention, as shown in FIG. 2 , the pressure regulating valve used in the present invention and the downstream pressure sensor form a closed-loop circuit, and the output value of the pressure regulating valve can be adjusted in real time according to the data of the pressure sensor. The advantage of this is to achieve accurate output of its own pressure through downstream pressure feedback, thereby improving the accuracy of pipeline flow regulation. Furthermore, after the wind tunnel test, the flame temperature can be precisely controlled according to the set working conditions of the temperature in the tank, so as to realize the ability of reheating. It greatly improves the test efficiency and saves resources.

Further, the valves in contact with the working medium of the present invention are all set as pneumatic valves driven by nitrogen. The advantage of this is to isolate the combustible gas from the air (or oxygen), and to isolate the combustible gas from the circuit. the possibility of danger.

On the basis of Embodiment 1, another embodiment of the present invention, as shown in Figure 4, the present invention also includes the construction method of the working medium supply system, which is introduced below through specific examples:

1) start

2) Determine the flow value Q or the range _Qmin - _Qmax required for each gas supply;

The flow parameters of air, natural gas, and oxygen that need to be satisfied in this embodiment:

3) Determine the path and branch number of each channel (branch) Venturi flowmeter

According to the supply gas temperature T ₀ , the gas source pressure P ₀ of the gas path, and the combustion chamber pressure P, the natural gas point and empty point Venturi flowmeter DN is determined, and the number of each branch of the natural gas main path, the air main path, and the air cooling path is determined. N and the diameter of each Venturi flowmeter DN.

The pressure of the upstream gas source that the embodiment can provide

Air natural gas oxygen Upstream air pressure 18-18.5MPa 2.0-2.1MPa 13-13.5MPa

As we all know, gas has an important feature, that is, it can be accelerated through a variable-section pipe, so that the speed of sound is formed at the throat (that is, where the pipe cross-section is the smallest), and the flow characteristics are shown in Figure 3. For the gas flow with the sound velocity in the throat, the flow rate, total temperature, total pressure and throat diameter have a certain relationship:

In the formula, Q _m is the mass flow rate, kg/s; C is the outflow coefficient; P ₀ is the absolute stagnation pressure at the inlet, Pa; T ₀ is the absolute stagnation temperature at the inlet, K; D is the throat of the Venturi flowmeter Diameter size, m;

In the calculation, C can be obtained by checking the physical properties of the gas. According to the flow requirement provided by the embodiment, T ₀ is selected at room temperature of 300K, and P ₀ or P ₀ -P _n is selected according to the above-mentioned pressure. From the above relationship, a range of throat diameters that satisfies the conditions can be obtained as follows:

Optional range of throat of empty point flowmeter: 0.94mm-2.63mm; optional range of throat of natural gas point flowmeter: 2.4mm-5.6mm; optional range of throat of oxygen flowmeter: 0.98mm-1.16mm; The main circuit can not meet the flow requirements. After iterative calculation, it can be divided into two branches: the optional range of the flowmeter is 0.86mm-2.14mm and 0.86mm-2.14mm respectively; the optional range of the air-cooled oxygen path flowmeter throat 1.72mm-4.36mm.

4) Select the flow meter and calculate the upstream pressure regulation value

Determine the pressure regulating range P ₀ -P _n of the pressure regulating valve according to the upstream air source pressure of each branch, the diameter DN of the venturi flowmeter, and the required flow range Q ₀ -Q _n .

Considering the convenience of processing technology and throat measurement, the throat diameter should be selected as an integer value as much as possible, and then brought into the relationship to calculate whether the upstream pressure can meet the conditions:

The relationship is based on the fluid mechanics model, continuity equation, Bernoulli equation, ISO9300 gives the critical flow Venturi mass flow calculation formula:

It is derived and converted into SI units using the customary length, mass, and pressure units of the wind tunnel test. The calculation is convenient and the results can be obtained quickly and accurately without affecting the calculation accuracy.

The throat of the empty point flowmeter is set to 2mm, and when the flow rate is 25g/s, the fixed pressure reducing valve is 3.45MPa; the throat of the natural gas point flowmeter is set to 2mm, and the flow rate is 1.5g/s, the fixed pressure reducing valve is 1.40MPa ; When the throat of the oxygen flowmeter is set to 1.1mm and the flow rate is 10g/s-25g/s, the pressure adjustment range of the pressure regulating valve is 2.17MPa-10.08MPa; the throat of the air-main 1-way flowmeter is set to 2mm, and the flow rate is When the flow rate is 25g/s-120g/s, the adjustment range of the pressure regulating valve is 3.45MPa-16.4MPa; when the throat of the air-main 2-way flowmeter is set to 4mm, and the flow rate is 120g/s-350g/s, the adjustment range of the pressure regulating valve is 4.13MPa-12.04MPa; when the air-cooled flowmeter throat is set to 4mm and the flow rate is 100g/s-400g/s, the adjustment range of the pressure regulating valve is 3.44MPa-13.76MPa; the natural gas 1-way flowmeter throat is set to 5mm, When the flow rate is 1.5g/s-6g/s, the adjustment range of the pressure regulating valve is 0.5MPa-2MPa; when the throat of the natural gas 2-way flowmeter is set to 10mm, and the flow rate is 6g/s-20g/s, the adjustment range of the pressure regulating valve It is 0.5MPa-1.67MPa. Organize the following table:

5) Determine the diameter of each pipeline and the Cv value of the pressure regulating valve

Determine the diameter of pipeline and switch valve, Cv value of pressure regulating valve, range of pressure sensor, etc.

In the case of constant temperature, the relationship can be obtained from the ideal gas equation

This relational expression is derived from the ideal gas equation, and is converted into SI units using the customary length, mass, and pressure units of the wind tunnel test. The calculation results are convenient and the results can be obtained quickly and accurately without affecting the calculation results.

In the formula, ρ is the gas density, kg/m ² ; M is the gas molar mass, mol; P is the gas pressure, MPa; 22.4 is the ideal gas molar volume, L; 0.1 is the gas pressure under standard conditions, MPa. The gas density at different pressures can be obtained from the above relationship, and the obtained density is brought into the relationship between flow rate and flow rate:

In the formula, D is the pipe diameter, m; Q _m is the gas flow rate, kg/s; v is the gas flow rate, m/s; ρ is the gas density, kg/m ² . With reference to the national standards "Oxygen and Related Gas Safety Technical Regulations GB16912-1997", "GB50184-2011 Industrial Metal Pipeline Engineering Construction Quality Acceptance Specifications", "Pressure Pipeline Supervision and Inspection Rules TSGD7006-2020" and the use of the implementation site, the above relationship can be determined. The pipe diameter is obtained after the flow rate:

Considering the convenience of system procurement and maintenance, the DN of the air main 2 and the air cooling circuit is selected as 20mm.

The Cv value is used to represent the flow coefficient of the control valve, which has the following formula:

1. When P ₁ < 2P _{2 2.} When P ₁ ≥ 2P ₂

In the formula, Q _g flow rate (under the condition of 760mmHgabs, 15.6 ℃), ft ³ /min; S _g specific gravity, air is 1, others are calculated according to approximate molecular weight; P ₁ inlet absolute pressure, bar; P2, outlet absolute pressure, bar ; Differential pressure ΔP=P1-P2. According to the relational expression, the Cv value of the pressure regulating valve can be obtained initially.

6) End.

Fig. 5 is the heating data of an effective test of the present invention. It can be seen from the figure that the temperature rises smoothly and continuously during the heating process. It realizes the function of stepless adjustment of flow within the range. It also realizes the precise control of typical working conditions and the ability to reheat after wind tunnel test, which greatly improves the test efficiency. The invention has clear principle, simple structure and easy realization, and has extremely high application value.

The above is not a limitation of the present invention, it should be pointed out: for those skilled in the art, under the premise of not departing from the essential scope of the present invention, several changes, modifications, additions or replacements can also be made. Improvements and modifications should also be considered within the scope of the present invention.

Claims (7)

1. A working medium supply system for a heat storage heater in a wind tunnel experiment is characterized by comprising a natural gas point path, an air point path, a natural gas main path, an air main path, an oxygen supplementing path, a cooling air path, a pressure sensor and a flame detector;

the natural gas point way and the air point way are respectively connected with the igniter, and natural gas and air with constant flow are conveyed to the igniter through the natural gas point way and the air point way;

the natural gas main road, the air main road and the oxygen supplement road are respectively connected with the main burner, wide-range flow is regulated through the natural gas main road and the air main road, oxygen input is provided for the ultra-high temperature working condition of the heat storage heater through the oxygen supplement road, the natural gas main road and the air main road comprise a plurality of branches with different flow coefficients, branches are added or reduced according to actual needs, the natural gas main road and the air main road are respectively provided with a gas transmission pipeline and a sensor for measuring gas source pressure, the sensor for measuring the gas source pressure is arranged in front of a valve, a plurality of branch pipelines are respectively arranged behind the valve, each branch comprises a pressure regulating valve group, a sensor group for measuring the pressure behind the valve and a throttling device, the medium pressure is regulated through the pressure regulating valve group, the sensor for measuring the pressure behind the valve is arranged at the downstream of the pressure regulating valve group, the throttling device is connected at the rear end of the valve, and the branches are converged into a pipeline behind the throttling device, the tail end of the gas transmission pipeline is connected with a check valve near the interface of the burner, and the downstream of the check valve is connected with the burner;

the cooling air path and the air point path are connected with the cooling burner; measuring the total pressure of an igniter through a pressure sensor, and detecting the main flame of a burner through a flame detector;

the throttling device is matched with an upstream pressure regulating valve to control the flow regulation of the single branch measuring range, the throttling device is a special device based on a sonic nozzle, the device sequentially comprises an upstream pipeline, a pressure stabilizing chamber, the sonic nozzle and a downstream pipeline along the airflow direction, the chamber is provided with a pressure sensor and a temperature sensor, the control of the pipeline flow is converted into the regulation of the chamber pressure through the throttling device, and the pressure sensor and the temperature sensor are used for respectively measuring the gas pressure and the temperature;

the pressure regulating valve and a downstream pressure sensor form a closed loop, and the output value of the pressure regulating valve is adjusted in real time according to the data of the pressure sensor; and valves in contact with the working medium are all set as pneumatic valves driven by nitrogen.

2. The working medium supply system for the heat storage heater in the wind tunnel experiment as claimed in claim 1, wherein the natural gas point path and the air point path are the same in structure and comprise a gas transmission pipeline, a sensor, a pressure reducing valve, a throttling device and a check valve, wherein the sensor is arranged in front of a valve and measures the pressure of a gas source through the sensor; the pressure reducing valve is arranged between the first valve and the second valve, the rear end of the second valve is connected with the throttling device, the tail end of the gas transmission pipeline is close to the burner interface and is connected with the check valve, and the downstream of the check valve is connected with the burner.

3. The working medium supply system for the wind tunnel experiment heat accumulation heater, according to claim 1, is characterized in that the igniter is set to be a fixed power igniter, a fixed value pressure reducing valve is adopted for a natural gas point circuit and an air point circuit, media with fixed flow and pressure are output from the natural gas point circuit and the air point circuit, and the system is used for realizing on-off of output of the media by controlling a switch valve.

4. The working medium supply system for the heat storage heater in the wind tunnel experiment according to claim 1, wherein the oxygen supply path comprises a gas transmission line, a pressure regulating valve g, a sensor i, a sensor j, a throttling device g and a check valve e, the sensor i for measuring the pressure of a gas source is arranged in front of the valve e, the pressure regulating valve g is arranged between the valve e and the valve f, the sensor j for measuring the pressure behind the valve is arranged at the downstream of the pressure regulating valve g, the throttling device g is connected behind the valve f, the check valve e is connected at the tail end of the gas transmission line close to the interface of the burner, and the check valve e is connected with the main air path through a tee joint.

5. The working medium supply system for the heat storage heater in the wind tunnel experiment is characterized in that the cooling air path comprises a gas transmission pipeline, a sensor k, a valve f, a pressure regulating valve h, a sensor l, a valve g, a throttling device h, a switch valve a, a switch valve b and a switch valve c, the sensor k for measuring the pressure of a gas source is arranged in front of the valve f, the pressure regulating valve h is arranged between the valve f and the valve g, the sensor l for measuring the pressure behind the valve is arranged at the downstream of the pressure regulating valve h, the rear end of the valve g is connected with the throttling device h, the tail of the gas transmission pipeline close to the interface of the combustor is connected with the inlet of a combustor cooling channel, the outlet of the combustor cooling channel is connected with the switch valve a through a pipeline, and the rear end of the switch valve a is discharged to the outside through a pipeline;

the cooling air path is divided into two paths at the outlet of the cooling channel of the burner through a tee joint, and one path is connected with a switch valve c and led to the outside; the other path is connected between the check valve d of the air main path and the burner through the back end of a switch valve b.

6. A working medium supply construction method for a heat storage heater for a wind tunnel experiment adopts the working medium supply system for the heat storage heater for the wind tunnel experiment as claimed in any one of claims 1 to 5, and is characterized by comprising the following steps:

(1) determining the flow value or range required by each path of air supply according to the test requirements;

(2) determining the drift diameter value range and the branch number of the Venturi flowmeter of each main path or branch according to the temperature of the gas supply, the pressure of the gas source and the pressure of the combustion chamber;

(3) selecting a drift diameter of the flowmeter, and checking a pressure regulating value or range of an upstream pressure regulating valve;

(4) and determining the drift diameters of the pipelines and the switching valves and the Cv value of the pressure regulating valve according to the maximum flow of each branch.

7. The working medium supply construction method for the wind tunnel experiment heat storage heater according to claim 6, wherein in the step (2), the working medium is supplied according to the temperature T of the supplied gas ₀ Gas source pressure P of gas circuit ₀ The combustion chamber pressure P determines the drift diameter DN of the Venturi flowmeters at the natural gas point and the dead point, determines the number N of the branch circuits of the natural gas main circuit, the air main circuit and the air cooling circuit and the drift diameter DN of each Venturi flowmeter, and accords with the relational expression for the gas flow of the throat forming sound velocity:

in the formula, Q _m Is the mass flow rate; c is an outflow coefficient; p ₀ Absolute stagnation pressure at the inlet; t is ₀ Absolute stagnation temperature at the inlet; d is the diameter size of the throat part of the Venturi flowmeter; and calculating the diameter range of the throat according to the relational expression.

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